JP6814617B2 - Organic electroluminescence device and its manufacturing method, display device, lighting device - Google Patents

Description

The present invention relates to an organic electroluminescence device (hereinafter, electroluminescence (electric field emission) may be referred to as "EL"), a method for manufacturing the same, a display device, and a lighting device.

The organic EL element has features such as being able to be driven at a low voltage, being thin, lightweight, and being flexible. Therefore, the organic EL element is suitably used for an image display device and a lighting device.
The organic EL element has a structure in which a plurality of layers such as an electron transport layer, a light emitting layer, and a hole transport layer are laminated between a cathode and an anode. Examples of the organic EL element include a forward structure in which an anode is arranged between the substrate and the light emitting layer, and a reverse structure in which a cathode is arranged between the substrate and the light emitting layer. In an organic EL element having an inverted structure, when it is used in an image display device or the like, a cathode and a transistor or the like can be easily connected.

In recent years, an organic-inorganic hybrid organic EL device (Hybrid Organic Inorganic LED: HOILED) having an inverse structure in which a metal oxide layer stable in the atmosphere and having a small work function is formed on the cathode surface has been proposed (for example, non-HOILED). See Patent Document 1 and Non-Patent Document 2). In such an organic EL device, the electron injection property is improved by providing the metal oxide layer.
Examples of metal oxides include titanium oxide (TiO ₂ ), zinc oxide (ZnO), tungsten oxide (WO ₃ ), niobium oxide (Nb ₂ O ₅ ), iron oxide (Fe ₂ O ₃ ), and tin oxide (SnO ₂ ). Etc. can be used (see, for example, Patent Document 1 and Patent Document 2).

The metal oxide layer is generally formed by a sputtering method. However, when the metal oxide layer is formed by the sputtering method, heat treatment at a high temperature is required.
As a method of forming a metal oxide layer at a low temperature, there is a method of applying zinc acetylacetonate and heat-treating it. For example, Non-Patent Document 3 describes a film forming method in which zinc acetylacetonate is applied and heat-treated at 120 degrees.

Japanese Unexamined Patent Publication No. 2012-4492 JP-A-2007-53286 Japanese Unexamined Patent Publication No. 2013-239961 Japanese Unexamined Patent Publication No. 2014-168014 Japanese Unexamined Patent Publication No. 2011-184430 Japanese Unexamined Patent Publication No. 2012-151148

APPLIED PHYSICS LETTERS Volume89, page183510 (2006) Advanced Materials Volume23, page1829 (2011) Advanced Materials Volume26, page2750 (2014) H.Cho et al., Science, vol.350, p.1222 (2015)

However, an organic EL device having an inverted structure having an electron injection layer made of a metal oxide layer has a problem that when it is continuously driven, its light emitting characteristics deteriorate in a short time and its light emitting brightness decreases.
The present invention has been made in view of the above circumstances, and an object of the present invention is to provide an organic EL device having an inverted structure in which the light emitting characteristics are less likely to deteriorate even when continuously driven, and a method for manufacturing the same.
Another object of the present invention is to provide a display device and a lighting device that include the above-mentioned organic EL element and can be used stably for a long period of time.

In order to solve the above problems, the present inventor has made extensive studies as shown below.
First, regarding the cause of deterioration of light emission characteristics in a short time when a metal oxide layer formed by a method of applying zinc acetylacetonate and heat treatment is continuously driven in an organic EL device having an inverted structure used as an electron injection layer. investigated.
As a result, it was found that the cause of the deterioration of the light emitting characteristics is that the surface roughness of the electron injection layer made of the metal oxide layer on the light emitting layer side is large. In an organic EL device having a reverse structure, if the surface roughness of the electron injection layer on the light emitting layer side is large, it adversely affects each layer formed on the electron injection layer. Specifically, it is presumed that the leakage current in the organic EL element increases, the number of defects at the interface on the light emitting layer side of the electron injection layer increases, and the deterioration of the light emitting characteristics is promoted.

Therefore, the present inventor investigated the reason why the surface roughness of the metal oxide layer becomes large. As a result, it was found that this is because a large number of large aggregates composed of metal oxides are present in the metal oxide layer. The present inventor has diligently studied to suppress the formation of agglomerates of metal oxides and to form a metal oxide layer having a small surface roughness. As a result, it has been found that a layer containing a metal oxide may be formed by a method of applying a solution containing a metal salt and a tertiary amine and heat-treating the solution.

In the above method, since the tertiary amine is contained in the solution to be applied, aggregation of metal salts in the solution and in the coating film obtained by applying the same is suppressed. As a result, aggregation of the metal oxide in the layer containing the metal oxide obtained by heat-treating the coating film is suppressed, and a layer containing the flat metal oxide can be obtained. Further, the tertiary amine has an electron donating property and is suitable as a material for an electron injection layer.

The present inventor has made further diligent studies and used a layer containing a flat metal oxide formed by the above method as an electron injection layer, so that the light emission characteristics deteriorate even when continuously driven with high brightness and high efficiency. After confirming that an organic EL device having an inverted structure that is difficult to obtain can be obtained, the present invention was conceived.

That is, the present invention relates to the following invention.
[1] The substrate, cathode, electron injection layer, light emitting layer, and anode are arranged in this order.
The electron injection layer comprises a mixture containing at least a metal oxide and a tertiary amine.
An organic electroluminescence device characterized in that the surface roughness Ra on the light emitting layer side is 2.5 nm or less.

[2] The organic electroluminescence device according to [1], wherein the metal oxide is zinc oxide.
[3] The organic electroluminescence device according to [1] or [2], wherein the tertiary amine is 2-dimethylaminopyridine.

[4] The organic electroluminescence device according to any one of [1] to [3], wherein a hole injection layer is provided between the light emitting layer and the anode.
[5] The organic electroluminescence device according to [4], wherein a hole transport layer is provided between the light emitting layer and the hole injection layer.
[6] The organic electroluminescence according to any one of [1] to [5], wherein an organic electron injection layer made of an organic material is provided between the light emitting layer and the electron injection layer. element.
[7] The organic electroluminescence device according to any one of [1] to [6], wherein the substrate is made of a resin material.

[8] A display device including the organic electroluminescence device according to any one of [1] to [7].
[9] A lighting device including the organic electroluminescence device according to any one of [1] to [7].

[10] A method for manufacturing an organic electroluminescence device in which a cathode, an electron injection layer, a light emitting layer, and an anode are formed in this order on a substrate.
The step of forming the electron injection layer is a coating step of applying a solution containing a metal salt and a tertiary amine to the surface to be formed of the electron injection layer, and a heat treatment of the surface to be formed to which the solution is applied. A method for producing an organic electroluminescence element, which comprises a heat treatment step of forming the electron injection layer composed of a mixture containing at least a metal oxide and a tertiary amine.

[11] The method for producing an organic electroluminescence device according to [10], wherein the metal salt is a zinc acetylacetonate complex and the tertiary amine is 2-dimethylaminopyridine.

The organic EL device of the present invention has an inverse structure, the electron injection layer is composed of a mixture containing at least a metal oxide and a tertiary amine, and the surface roughness Ra on the light emitting layer side is 2.5 nm or less. Since the organic EL device of the present invention has an electron injection layer composed of a mixture containing at least a metal oxide and a tertiary amine, the electron injection property is good, and the brightness and efficiency are high. Moreover, since the surface of the electron injection layer on the light emitting layer side is flat, deterioration of the light emitting characteristics due to the large surface roughness on the light emitting layer side of the electron injection layer can be suppressed. Therefore, the organic EL element of the present invention is unlikely to deteriorate in light emission characteristics even when continuously driven. Further, the organic EL element of the present invention does not necessarily have to be tightly sealed because the light emitting characteristics are not easily deteriorated.
Since the display device and the lighting device of the present invention include the organic EL element of the present invention, they can be used stably for a long period of time.

Further, the method for producing an organic EL element of the present invention is a method for producing an organic EL element having an inverted structure, and a step of forming an electron injection layer is a method of forming a solution containing a metal salt and a tertiary amine in the electron injection layer. A coating step of applying to the surface to be formed and a heat treatment step of heat-treating the surface to be formed to which the solution is applied to form the electron-injected layer composed of a mixture containing at least a metal oxide and a tertiary amine. including. Therefore, the obtained electron-injected layer has a metal in the electron-injected layer as compared with the case where, for example, a solution containing no tertiary amine in which a metal salt is dispersed and / or dissolved in a solvent is applied and heat-treated. Aggregation of oxides is suppressed and the surface becomes flat.

It is sectional drawing for demonstrating an example of the organic EL element of this embodiment. It is a graph which shows the relationship between the applied voltage and the current density of each organic EL element of an Example and a comparative example. It is a graph which shows the relationship between the applied voltage and the luminance of each organic EL element of an Example and a comparative example. It is a graph which shows the relationship between the current density and the external quantum efficiency of each organic EL element of an Example and a comparative example. It is a graph which showed the relationship between the elapsed time from the start of driving with a constant current, and the relative brightness by using an organic EL life measuring apparatus. It is an atomic force microscope observation photograph which shows the surface shape of the electron injection layer of an Example. It is an atomic force microscope observation photograph which shows the surface shape of the electron injection layer of a comparative example.

Hereinafter, the organic EL element of the present invention, its manufacturing method, a display device, and a lighting device will be described in detail with reference to the drawings.
"Organic EL element"
FIG. 1 is a schematic cross-sectional view for explaining an example of the organic EL element of the present embodiment. The organic EL element 10 of the present embodiment shown in FIG. 1 has a laminated structure including a light emitting layer 6 formed between an anode 9 (electrode) and a cathode 3 (electrode).

The laminated structure of the organic EL element 10 of the present embodiment includes an electron injection layer 1, an organic electron injection layer 4, an electron transport layer 5, a light emitting layer 6, a hole transport layer 7, and a hole injection layer 8. Are formed in this order. The organic EL element 10 of the present embodiment has an inverted structure in which the cathode 3 is arranged between the substrate 2 and the light emitting layer 6. Further, the organic EL element 10 of the present embodiment is an organic-inorganic hybrid organic EL element having an inverse structure in which the electron injection layer 1 contains a metal oxide which is an inorganic material.

The organic EL element 10 shown in FIG. 1 may be a top emission type that extracts light on the side opposite to the substrate 2, or may be a bottom emission type that extracts light on the substrate 2 side.

In the organic EL element 10 of the present embodiment, the material forming each layer may be a low molecular weight compound, a high molecular weight compound, or a mixture thereof.
In the present invention, the low molecular weight compound means a material that is not a high molecular weight compound (polymer) and does not necessarily mean an organic compound having a low molecular weight.

(substrate)
Examples of the material of the substrate 2 include a resin material and a glass material. As the material of the substrate 2, only one kind may be used, or two or more kinds may be used in combination.
Examples of the resin material used for the substrate 2 include polyethylene terephthalate (PET), polyethylene naphthalate (PEN), cycloolefin polymer, polyamide, polyether sulfone, polymethylmethacrylate, polycarbonate, polyarylate and the like. When a resin material is used as the material of the substrate 2, the organic EL element 10 having excellent flexibility can be obtained, which is preferable.
Examples of the glass material used for the substrate 2 include quartz glass and soda glass.

When the organic EL element 10 is a bottom emission type, a transparent substrate is used as the material of the substrate 2.
When the organic EL element 10 is a top emission type, not only a transparent substrate but also an opaque substrate may be used as the material of the substrate 2. Examples of the opaque substrate include a substrate made of a ceramic material such as alumina, a substrate having an oxide film (insulating film) formed on the surface of a metal plate such as stainless steel, and a substrate made of a resin material.

The average thickness of the substrate 2 is preferably 0.1 to 30 mm, more preferably 0.1 to 10 mm.
The average thickness of the substrate 2 can be measured with a digital multimeter, calipers, or the like.

(cathode)
The material of the cathode 3, ITO (indium tin oxide), IZO (indium zinc oxide), FTO (fluorine tin oxide), InSnZnO (indium zinc tin _{oxide, ITZO), In 3 O 3} , SnO 2, Sb -containing SnO ₂ , Al-containing ZnO and other oxide conductive materials are preferably used. Among these, it is particularly preferable to use ITO, IZO, and FTO as the material of the cathode 3.

The average thickness of the cathode 3 is not particularly limited, but is preferably 10 to 500 nm, and more preferably 100 to 200 nm.

(Electron injection layer)
The electron injection layer 1 is composed of a mixture containing at least a metal oxide and a tertiary amine.
The metal oxide preferably contains any one element of indium, gallium, zinc, tin, aluminum, silicon, manganese, titanium, molybdenum, magnesium, calcium, zirconium and hafnium. The metal oxide contained in the electron injection layer 1 is preferably zinc oxide because it has excellent electron injection properties.

Examples of the tertiary amine include aliphatic amines such as 2-dimethylaminopyridine (2-DMAP), N-butyldimethylamine, N, N-dipropylethylamine, and polyethyleneimine represented by the following general formula (1), and N. , N-Dimethylaniline, aromatic amines such as 4-dimethylaminopyridine and the like can be used. As the tertiary amine contained in the electron injection layer 1, 2-dimethylaminopyridine is particularly preferable. Since 2-dimethylaminopyridine has good electron injectability and is a liquid at normal temperature and pressure, it is easily and uniformly dispersed in a solution containing an acetylacetonate metal complex and a tertiary amine in the production method described later. , Effectively suppresses aggregation of metal oxides in the electron injection layer 1. Therefore, the electron injection layer 1 has a flat surface on the light emitting layer 6 side.

The ratio of the metal oxide to the tertiary amine in the mixture forming the electron injection layer 1 is preferably 0.5 to 400% by mass of the tertiary amine with respect to 100% by mass of the metal oxide. When the ratio of the metal oxide to the tertiary amine is in the above range, deterioration of the light emitting characteristics can be suppressed more effectively. The ratio of the metal oxide to the tertiary amine is more preferably 3 to 200% by mass, still more preferably 80 to 120% by mass.

The surface roughness Ra on the light emitting layer 6 side of the electron injection layer 1 is 2.5 nm or less, preferably 2.0 nm or less, and more preferably 1.5 nm or less. If the surface roughness Ra on the light emitting layer 6 side of the electron injection layer 1 exceeds 2.5 nm, the leak current in the organic EL element 10 and / or the defect at the interface on the light emitting layer 6 side of the electron injection layer 1 cannot be sufficiently suppressed. , The light emitting characteristics tend to deteriorate.
The surface roughness Ra on the light emitting layer 6 side of the electron injection layer 1 can be measured by using the X-ray reflectivity (XRR) method.

The average thickness of the electron injection layer 1 is not particularly limited, but is preferably 1 to 1000 nm, and more preferably 2 to 100 nm. When the average thickness of the electron injection layer 1 is 1 nm or more, the effect of having the electron injection layer 1 can be sufficiently obtained. Further, when the average thickness of the electron injection layer 1 is 1000 nm or less, the electron injection layer 1 can be efficiently formed.
The average thickness of the electron injection layer 1 can be measured by a stylus type step meter and spectroscopic ellipsometry.

(Organic electron injection layer)
Examples of the material of the organic electron injection layer 4 include polyacetylene compounds such as trans-type polyacetylene, cis-type polyacetylene, poly (di-phenylacetylene) (PDPA), and poly (alkyl, phenylacetylene) (PAPA); Para-phenylene) (PPV), poly (2,5-dialkoxy-para-phenylene vinylene) (RO-PPV), cyano-substituted-poly (para-phenylene) (CN-PPV), poly (2- Polyparaphenylene vinylene compounds such as dimethyloctylsilyl-para-phenylene vinylene) (DMOS-PPV), poly (2-methoxy, 5- (2'-ethylhexoxy) -para-phenylene vinylene) (MEH-PPV); Polythiophene compounds such as poly (3-alkylthiophene) (PAT), poly (oxypropylene) triol (POPT); poly (9,9-dialkylfluorene) (PDAF) such as poly (9,9-dioctylfluorene) , Poly (dioctylfluorene-alto-benzothiazol) (F8BT), α, ω-bis [N, N'-di (methylphenyl) aminophenyl] -poly [9,9-bis (2-ethylhexyl) fluorene-2 , 7-Zill] (PF2 / 6am4), polyfluorene compounds such as poly (9,9-dioctyl-2,7-dibinylene fluorenyl-ortho-co (anthracene-9,10-diyl); poly Polyparaphenylene compounds such as (para-phenylene) (PPP), poly (1,5-dialkoxy-para-phenylene) (RO-PPP); poly (N-vinylcarbazole) (PVK). Carbazole-based compounds; polysilane-based compounds such as poly (methylphenylsilane) (PMPS), poly (naphthylphenylsilane) (PNPS), poly (biphenylylphenylsilane) (PBPS), and boron-containing compounds described in Patent Document 3. Examples thereof include compounds and polyamines described in Patent Document 4. One type of these may be used, or two or more types may be used.

The average thickness of the organic electron injection layer 4 is preferably 5 to 100 nm, more preferably 10 to 60 nm.
The average thickness of the organic electron injection layer 4 can be measured by a stylus type step meter and spectroscopic ellipsometry. Alternatively, it can be measured at the time of film formation with a crystal oscillator film thickness meter.

(Electronic transport layer)
As the material of the electron transport layer 5, any material that can be usually used as the material of the electron transport layer 5 can be used, and these may be mixed and used.
Examples of low molecular weight compounds that can be used as materials for the electron transport layer 5 include bis [2- (o-hydroxyphenylbenzothiazole] zinc (II) (ZnBTZ2), boron-containing compounds, Tris-1,3,5. -Pyridine derivatives such as (3'-(pyridine-3''-yl) phenyl) benzene (TmPyPhB), quinoline derivatives such as (2- (3- (9-carbazolyl) phenyl) quinoline (mCQ)), 2-Phenyl-4,6-bis (3,5-dipyridylphenyl) Pyrimidine derivatives such as pyrimidin (BPyPPM), pyrazine derivatives, phenanthroline derivatives such as vasophenantroline (BPhen), 2,4-bis (4-biphenyl) ) -6- (4'-(2-pyridinyl) -4-biphenyl)-[1,3,5] Triazine derivatives such as triazine (MPT), 3-phenyl-4- (1'-naphthyl) -5 -Triazole derivatives such as phenyl-1,2,4-triazole (TAZ), oxazole derivatives, 2- (4-biphenylyl) -5- (4-tert-butylphenyl-1,3,4-oxadiazole) Oxaziazole derivatives such as (PBD), imidazoles such as 2,2', 2''-(1,3,5-ventryyl) -tris (1-phenyl-1-H-benzimidazole) (TPBI) Derivatives, aromatic ring tetracarboxylic acid anhydrides such as naphthalene and perylene, bis [2- (2-hydroxyphenyl) benzothiazolate] zinc (Zn (BTZ) ₂ ), tris (8-hydroxyquinolinato) aluminum (Alq ₃ ), etc. Various metal complexes typified by, sylrole derivatives such as 2,5-bis (6'-(2', 2 ″ -bipyridyl)) -1,1-dimethyl-3,4-diphenylsilol (PyPySPyPy). Examples thereof include organic silane derivatives, and one or more of these can be used.
Among these, ZnBTZ2 is preferable.

The average thickness of the electron transport layer 5 is not particularly limited, but is preferably 10 to 150 nm, and more preferably 40 to 100 nm.
The average thickness of the electron transport layer 5 can be measured at the time of film formation with a crystal oscillator film thickness meter.

(Light emitting layer)
The material forming the light emitting layer 6 may be a low molecular weight compound, a high molecular weight compound, or a mixture thereof.

Examples of the polymer compound forming the light emitting layer 6 include polyacetylene compounds such as trans-type polyacetylene, cis-type polyacetylene, poly (di-phenylacetylene) (PDPA), and poly (alkylphenylacetylene) (PAPA); (Para-phenylene) (PPV), poly (2,5-dialkoxy-para-phenylene vinylene) (RO-PPV), cyano-substituted-poly (para-phenylene) (CN-PPV), poly (2) Polyparaphenylene vinylene compounds such as -dimethyloctylsilyl-para-phenylene vinylene) (DMOS-PPV), poly (2-methoxy, 5- (2'-ethylhexoxy) -para-phenylene vinylene) (MEH-PPV) Polythiophene compounds such as poly (3-alkylthiophene) (PAT), poly (oxypropylene) triol (POPT); poly (9,9-dialkylfluorene) (PDAF), poly (dioctylfluorene-alto-benzothiazol) ) (F8BT), α, ω-bis [N, N'-di (methylphenyl) aminophenyl] -poly [9,9-bis (2-ethylhexyl) fluorene-2,7-zil] (PF2 / 6am4) , Polyfluorene compounds such as poly (9,9-dioctyl-2,7-dibinylene fluorenyl-ortho-co (anthracene-9,10-diyl); poly (para-phenylene) (PPP), poly Polyparaphenylene compounds such as (1,5-dialkoxy-para-phenylene) (RO-PPP); polycarbazole compounds such as poly (N-vinylcarbazole) (PVK); poly (methylphenylsilane) Polysilane compounds such as (PMPS), poly (naphthylphenylsilane) (PNPS), poly (biphenylenephenylsilane) (PBPS); and the boron compound-based polymer compounds described in Patent Documents 5 and 6. Can be mentioned.

Examples of the low molecular weight compound forming the light emitting layer 6 include phosphorus light emitting materials, 8-hydroxyquinolin aluminum (Alq ₃ ), and tris [1-phenylisoquinolin-C2, N] iridium (III) (Ir (piq) ₃ ). ), Bis [2- (o-hydroxyphenylbenzothiazole] zinc (II) (ZnBTZ2) tris (4-methyl-8 quinolinolate) aluminum (III) (Almq ₃ ), 8-hydroxyquinolin zinc (Znq ₂ ), ( 1,10-phenanthroline) -Tris- (4,4,4-trifluoro-1- (2-thienyl) -butane-1,3-geonate) Europium (III) (Eu (TTA) ₃ (phen)), Various metal compounds such as 2,3,7,8,12,13,17,18-octaethyl-21H, 23H-porphin platinum (II); such as distyrylbenzene (DSB), diaminodistyrylbenzene (DADSB). Benzene-based compounds, naphthalene-based compounds such as Nile Red, phenanthrene-based compounds such as phenanthrene, chrysene, chrysene-based compounds such as 6-nitrochrysen, perylene, N, N'-bis (2,5- Di-t-butylphenyl) -3,4,9,10-perylene compounds such as perylene-di-carboxyimide (BPPC), coronene compounds such as coronen, anthracenes such as anthracene and bisstyrylanthracene Compounds, pyrene compounds such as pyrene, pyrane compounds such as 4- (di-cyanomethylene) -2-methyl-6- (para-dimethylaminostyryl) -4H-pyran (DCM), such as acrydin Aclysin compounds, Stilben compounds such as Stilben, 4,4'-bis [9-dicarbazolyl] -2,2'-biphenyl (CBP), 4,4'-bis (9-ethyl-3-carbazovinylene) -1 , Carbazole compounds such as 1'-biphenyl (BCzVBi), thiophene compounds such as 2,5-dibenzoxazolethiophene, benzoxazole compounds such as benzoxazole, benzoimidazole compounds such as benzoimidazole, 2, , 2'-(para-phenylenedivinylene) -benzothiazole compounds such as bisbenzothiazole, bistilyl (1,4-diphenyl-1,3-butadiene), butadiene compounds such as tetraphenylbutadiene, nafta Naphthalimide-based compounds such as luimide, coumarin-based compounds such as coumarin, perinone-based compounds such as perinone, oxadiazole-based compounds such as oxadiazole, aldazine-based compounds, 1, 2, 3, 4, 5 -Cyclopentadiene compounds such as pentaphenyl-1,3-cyclopentadiene (PPCP), quinacridone compounds such as quinacridone and quinacridone red, pyridine compounds such as spirolopyridine and thiadiazolopyridine, 2,2' , 7,7'-spiro compounds such as tetraphenyl-9,9'-spirobifluorene, phthalocyanine (H 2 _Pc), metal or metal-free phthalocyanine compound such as copper phthalocyanine and the like, these One kind or two or more kinds can be used.

As the light emitting layer 6, for example, an organic material that emits infrared light can be used in addition to the material that emits visible light. Further, as the material of the light emitting layer 6, in addition to the organic material, for example, a material having a perovskite structure represented by quantum dots or CH ₃ NH ₃ PbBr ₃ (see, for example, Non-Patent Document 4) may be used. Good. As the material of the light emitting layer 6, a thermally activated delayed fluorescent material may be used in addition to the fluorescent material and the phosphorescent material.

The average thickness of the light emitting layer 6 is not particularly limited, but is preferably 10 to 150 nm, more preferably 20 to 100 nm.
The average thickness of the light emitting layer 6 can be measured by a crystal oscillator film thickness meter when the material of the light emitting layer 6 is a low molecular weight compound. When the material of the light emitting layer 6 is a polymer compound, it can be measured by a contact type step meter.

(Hole transport layer)
As the material of the hole transport layer 7, any material that can be usually used as the material of the hole transport layer 7 can be used, and these may be mixed and used.

Materials for the hole transport layer 7 include N4, N4'-bis (dibenzo [b, d] thiophen-4-yl) -N4, N4'-diphenylbiphenyl-4,4'-diamine (DBTPB), 1, Arylcycloalkane compounds such as 1-bis (4-di-para-triaminophenyl) cyclohexane, 1,1'-bis (4-di-para-trilaminophenyl) -4-phenyl-cyclohexane, 4,4', 4''-trimethyltriphenylamine, N, N, N', N'-tetraphenyl-1,1'-biphenyl-4,4'-diamine, N, N'-diphenyl-N, N'-bis (3-methylphenyl) -1,1'-biphenyl-4,4'-diamine (TPD1), N, N'-diphenyl-N, N'-bis (4-methoxyphenyl) -1, 1'-biphenyl-4,4'-diamine (TPD2), N, N, N', N'-tetrakis (4-methoxyphenyl) -1,1'-biphenyl-4,4'-diamine (TPD3), N, N'-di (1-naphthyl) -N, N'-diphenyl-1,1'-biphenyl-4,4'-diamine (α-NPD), arylamine compounds such as TPTE, N, N , N', N'-tetraphenyl-para-phenylenediamine, N, N, N', N'-tetra (para-tolyl) -para-phenylenediamine, N, N, N', N'-tetra (meta) -Trill) -Phenylene diamine compounds such as meta-phenylenediamine (PDA), carbazole compounds such as carbazole, N-isopropylcarbazole, N-phenylcarbazole, stilben, 4-di-para-tolylaminostilben. Stilben compounds, oxazole compounds such as OxZ, triphenylmethanes, triphenylmethane compounds such as m-MTDATA, pyrazoline compounds such as 1-phenyl-3- (para-dimethylaminophenyl) pyrazoline, Benzine (cyclohexadiene) -based compounds, triazole-based compounds such as triazole, imidazole-based compounds such as imidazole, 1,3,4-oxadiazol, 2,5-di (4-dimethylaminophenyl) -1,3 , Oxaziazole compounds such as 4,-oxadiazole, anthracene, anthracene compounds such as 9- (4-diethylaminostyryl) anthracene, fluorenone, 2,4,7, -trinitro-9-fluorenone, 2 , 7-bis (2) -Hydroxy-3- (2-chlorophenylcarbamoyl) -1-naphthylazo) Fluolenone compounds such as fluorenone, aniline compounds such as polyaniline, silane compounds, 1,4-dithioketo-3,6-diphenyl-pyrrolo- (3,4-c) Pyrrole compounds such as pyrolopyrrole, fluorene compounds such as fluorene, porphyrin, porphyrin compounds such as metal tetraphenylporphyrin, quinacridone compounds such as quinacridone, phthalocyanines, copper phthalocyanines, Metallic or metal-free phthalocyanine compounds such as tetra (t-butyl) copper phthalocyanine, iron phthalocyanine, metal or metal-free phthalocyanine compounds such as copper naphthalocyanine, vanadyl naphthalocyanine, monoclonal gallium naphthalocyanine, N, Examples thereof include benzidine compounds such as N'-di (naphthalen-1-yl) -N, N'-diphenyl-benzidine, N, N, N', N'-tetraphenylbenzidine, and one of these or one of them. Two or more types can be used.
Among these, arylamine compounds such as DBTPB, α-NPD, and TPTE are preferable.

The average thickness of the hole transport layer 7 is not particularly limited, but is preferably 10 to 150 nm. More preferably, it is 40 to 100 nm.
The average thickness of the hole transport layer 7 can be measured at the time of film formation with a crystal oscillator film thickness meter.

(Hole injection layer)
The hole injection layer 8 may be made of an inorganic material or an organic material.
When the hole injection layer 8 is an organic material, the material of the hole injection layer 8 is, for example, tetrafluorotetracyanoquinodimethane (F4TCNQ) and / or 1,4,5,8,9,12-hexaazatriphenylene. -2,3,6,7,10,11-hexacarbonitrile (HAT-CN) and the like can be used.

When the hole injection layer 8 is an inorganic material, the hole injection layer 8 may be made of vanadium oxide (V ₂ O ₅ ), molybdenum trioxide (molybdenum oxide: MoO ₃ ), ruthenium oxide (RuO ₂ ), or the like. It is preferable to use one kind or two or more kinds of oxides. Among these, it is particularly preferable that vanadium oxide or molybdenum oxide is the main component.

The average thickness of the hole injection layer 8 is not particularly limited, but is preferably 1 to 1000 nm, more preferably 5 to 50 nm.
The average thickness of the hole injection layer 8 can be measured at the time of film formation with a crystal oscillator film thickness meter.

(anode)
Examples of the material of the anode 9 include Au, Pt, Ag, Cu, Al, and alloys containing these. Among these, it is preferable to use any one of Au, Ag, and Al as the material of the anode 9.

The average thickness of the anode 9 is not particularly limited, but is preferably, for example, 10 to 1000 nm, and more preferably 30 to 150 nm.
When the organic EL element 10 is a top emission type, it is preferable to use a transparent material as the material of the anode 9. When the organic EL element 10 is of the top emission type and an opaque material for irradiation light is used as the material of the anode 9, it can be used as the transparent anode 9 by setting the average thickness to about 10 to 30 nm.
The average thickness of the anode 9 can be measured at the time of film formation with a crystal oscillator film thickness meter.

In the organic EL element 10 of the present embodiment, the substrate 2, the cathode 3, the electron injection layer 4, the light emitting layer 6, and the anode 9 are arranged in this order, and the electron injection layer 1 contains at least a metal oxide and a tertiary amine. It is composed of a mixture containing the mixture, and has a surface roughness Ra on the light emitting layer 6 side of 2.5 nm or less. Since the organic EL device 10 of the present embodiment has an electron injection layer 1 composed of a mixture containing at least a metal oxide and a tertiary amine, the electron injection property is good, and the brightness and efficiency are high. Moreover, since the surface of the electron injection layer 1 on the light emitting layer 6 side is flat, it is possible to suppress deterioration of the light emitting characteristics due to the large surface roughness of the electron injection layer 1 on the light emitting layer 6 side. Therefore, the organic EL element 10 of the present embodiment is unlikely to deteriorate in light emission characteristics even when continuously driven. Further, since the organic EL element 10 of the present embodiment does not easily deteriorate in light emitting characteristics, it is not always necessary to strictly seal the organic EL element 10. Therefore, the organic EL element 10 of the present embodiment can be suitably used as a material for a display device, a lighting device, and the like.

"Manufacturing method of organic EL element"
In the present embodiment, as an example of the method for manufacturing the organic EL device of the present invention, the method for manufacturing the organic EL device 10 shown in FIG. 1 will be described as an example.
The organic EL element 10 shown in FIG. 1 has a cathode 3, an electron injection layer 1, an organic electron injection layer 4, an electron transport layer 5, a light emitting layer 6, and a hole transport layer 7 on a substrate 2. It can be manufactured by forming the hole injection layer 8 and the anode 9 in this order.

In the present embodiment, the steps of forming the electron injection layer 1 include a coating step of applying a solution containing a metal salt and a tertiary amine to the surface to be formed of the electron injection layer 1 and a surface to be formed to which the solution is applied. A heat treatment step of forming an electron injection layer 1 composed of a mixture containing at least a metal oxide and a tertiary amine is included.

Examples of metal salts include acetates such as zinc acetate, magnesium acetate, molybdenum acetate and calcium acetate, nitrates such as zinc nitrate and aluminum nitrate, carbonates such as zinc carbonate and manganese carbonate, and sulfuric acid such as tin sulfate and hafnium sulfate. Examples include salts, alkoxide metal complexes such as tetraethoxysilane and titanium tetraisopropoxide, acetylacetonate metal complexes such as zinc acetylacetonate complex, zirconium acetylacetonate complex, indium acetylacetonate complex, and gallium acetylacetonate complex. Be done. Among these metal salts, a zinc acetylacetonate complex is preferable because a metal oxide can be formed by low-temperature heat treatment.
The "metal salt" in the present embodiment means one containing a metal salt and a metal complex.

The solution containing the metal salt and the tertiary amine can be a solution consisting of the metal salt and the tertiary amine and a solvent for dispersing and / or dissolving them. The solvent can be determined according to the type of metal salt and / or tertiary amine, and for example, ethanol, methanol, isopropanol, toluene, xylene, tetrahydrofuran (THF), chloroform, toluene, cyclopentanone and the like can be used. Further, the solution containing the metal salt and the tertiary amine may contain, if necessary, a dispersant or the like in addition to the metal salt, the tertiary amine and the solvent. Further, the solution containing the metal salt and the tertiary amine may be a solution containing only the metal salt and the tertiary amine when the metal salt and / or the tertiary amine is a liquid at normal temperature and pressure.

The method for producing a solution containing a metal salt and a tertiary amine is not particularly limited, and for example, a metal salt solution composed of a metal salt and a solvent and an amine solution composed of a tertiary amine and a solvent are optional. It can be manufactured by a method of mixing at the ratio of. The solvent in the metal salt solution and the solvent in the amine solution may be the same or different.

The heat treatment step is performed to convert a part or all of the metal salt (precursor) into a metal oxide. That is, the electron injection layer 1 obtained after the heat treatment step may be a mixture containing only a metal oxide and a tertiary amine, or may be a mixture containing a metal salt, a metal oxide and a tertiary amine. ..

The heat treatment temperature and heat treatment time in the heat treatment step are determined according to the metal salt used. For example, when a zinc acetylacetonate complex is used as the metal salt, the heat treatment temperature is preferably in the range of 100 to 250 ° C, more preferably in the range of 120 to 150 ° C. By setting the heat treatment temperature to 100 ° C. or higher, the zinc acetylacetonate complex can be efficiently changed to zinc oxide. When the heat treatment temperature is 250 ° C. or lower, deformation of the substrate 2 can be sufficiently prevented when a substrate 1 made of a resin material is used.
When a zinc acetylacetonate complex is used as the metal salt, the heat treatment time is preferably 15 seconds to 60 minutes, more preferably 30 seconds to 10 minutes. By setting the heat treatment time to 15 seconds or more, the zinc acetylacetonate complex can be sufficiently converted into zinc oxide. Further, if the heat treatment time exceeds 60 minutes, the effect of the heat treatment is saturated, so that it is preferably 60 minutes or less.

The cathode 3 of the organic EL element 10 shown in FIG. 1, the organic electron injection layer 4, the electron transport layer 5, the light emitting layer 6, the hole transport layer 7, the hole injection layer 8, and each layer of the anode 9. The forming method is not particularly limited, and various conventionally known forming methods can be appropriately used to form the layers according to the characteristics of the material used for each layer.

Specifically, for example, as a method for forming the cathode 3 and the anode 9 of the organic EL element 10 shown in FIG. 1, a sputtering method, a vacuum vapor deposition method, a sol-gel method, a spray pyrolysis (SPD) method, and an atomic layer deposition (ALD) are used. ) Method, vapor phase deposition method, liquid phase deposition method and the like.

As a method of forming each of the organic electron injection layer 4, the electron transport layer 5, the light emitting layer 6, the hole transport layer 7, and the hole injection layer 8, a coating method of applying an organic compound solution containing an organic compound to be each layer, Examples thereof include a vacuum vapor deposition method and an ESDUS (Evasorative Spray Depositionation from Ultra-dilute Solution) method. Among these forming methods, it is preferable to use the coating method.

The solvent used for preparing the coating solution to be coated by the coating method is not particularly limited as long as it can dissolve an organic compound, but is not particularly limited, but tetrahydrofuran (THF), toluene, xylene, chloroform, dichloromethane, dichloroethane, chlorobenzene, cyclopentanone. One kind or two or more kinds selected from the above can be used. Among these, THF, toluene, chloroform, dichloroethane and cyclopentanone are preferable.

The coating liquid preferably has an organic compound concentration of 0.05 to 10% by mass in the solvent. With such a concentration, it is possible to suppress the occurrence of coating unevenness and unevenness at the time of coating. The concentration of the organic compound in the solvent is more preferably 0.1 to 5% by mass, still more preferably 0.1 to 3% by mass.

When the coating method is used as the method for forming each of the above layers, the spin coating method, casting method, gravure coating method, bar coating method, roll coating method, dip coating method, spray coating method, screen printing method, offset printing method, and inkjet printing Various coating methods such as the method can be used. Of these, the spin coating method is preferable.

When any one of the electron transport layer 5, the hole transport layer 7, and the hole injection layer 8 is made of an inorganic material, the layer made of the inorganic material is, for example, a sputtering method, a vacuum deposition method, or the like. It can be formed by the method of.

The thickness of each layer forming the organic EL element 10 shown in FIG. 1 can be measured by using a stylus type step meter and spectroscopic ellipsometry. When each layer is formed by a vacuum vapor deposition method, the thickness of each layer can be measured at the time of film formation using a crystal oscillator film thickness meter.

The method for manufacturing the organic EL element 10 of the present embodiment is a manufacturing method in which the cathode 3, the electron injection layer 4, the light emitting layer 6 and the anode 9 are formed in this order on the substrate 2, and the electron injection layer 1 is formed. The steps are a coating step of applying a solution containing a metal salt and a tertiary amine to the surface to be formed of the electron injection layer 1 (on the cathode 3 in FIG. 1) and a heat treatment of the surface to be formed to which the solution is applied. This includes a heat treatment step of forming an electron injection layer 1 composed of a mixture containing at least a metal oxide and a tertiary amine. Therefore, the obtained electron injection layer 1 is in the electron injection layer 1 as compared with the case where, for example, a solution containing no tertiary amine in which a metal salt is dispersed and / or dissolved in a solvent is applied and heat-treated. Aggregation of metal oxides in the above is suppressed, and the surface becomes flat. Specifically, in the method for producing the organic EL device 10 of the present embodiment, for example, when a zinc acetylacetonate complex is used as the metal salt and 2-dimethylaminopyridine is used as the tertiary amine, the surface roughness Ra is increased. A flat electron injection layer 1 having a diameter of 1.5 nm or less can be obtained.

Further, in the method for producing the organic EL device 10 of the present embodiment, when the zinc acetylacetonate complex is used as the metal salt, the heat treatment temperature is lower than that when the metal oxide layer is formed by the sputtering method. Can form the electron injection layer 1. Therefore, if necessary, it is possible to use a substrate made of a resin material in order to realize a flexible organic EL element 10 having excellent flexibility.

"Other examples"
The organic EL device of the present invention is not limited to the organic EL device described in the above-described embodiment.
In the organic EL element 10 shown in FIG. 1, the organic electron injection layer 4, the electron transport layer 5, the hole transport layer 7, and the hole injection layer 8 may be formed as needed and may not be provided. ..
Further, even if each of the cathode 3, the organic electron injection layer 4, the electron transport layer 5, the light emitting layer 6, the hole transport layer 7, the hole injection layer 8, and the anode 9 is formed of one layer. It may be composed of two or more layers.

The organic EL element 10 shown in FIG. 1 includes a cathode 3, an electron injection layer 1, an organic electron injection layer 4, an electron transport layer 5, a light emitting layer 6, a hole transport layer 7, a hole injection layer 8, and an anode 9. It may have another layer between each layer. Specifically, an electron blocking layer or the like may be provided, if necessary, for the purpose of further improving the characteristics of the organic EL element.

"Display device"
The display device of the present embodiment displays an image using an element array group in which a plurality of organic EL elements are arranged. The display device of the present embodiment includes an organic EL element in which the light emitting characteristics are less likely to deteriorate even when continuously driven, and the light emitting brightness is less likely to be lowered. Therefore, it can be used stably for a long period of time.
"Lighting device"
The lighting device of the present embodiment performs surface emission using an element array group in which a plurality of organic EL elements are arranged. The lighting device of the present invention includes an organic EL element in which the light emitting characteristics are less likely to deteriorate even when continuously driven, and the light emitting brightness is less likely to be lowered. Therefore, it can be used stably for a long period of time.

Hereinafter, examples and comparative examples of the present invention will be described. The present invention is not limited to the examples shown below.

<Example>
The organic EL element 10 having the reverse structure shown in FIG. 1 was manufactured by the method shown below.
[1] A commercially available transparent glass substrate (hereinafter, also simply referred to as a substrate) 2 having an average thickness of 0.7 mm and having a cathode 3 made of an ITO film (patterned to a film thickness of 150 nm and a width of 3 mm) was prepared.

[2] Next, the substrate 2 having the cathode 3 was ultrasonically washed in acetone and isopropanol for 10 minutes, and then boiled in isopropanol for 5 minutes. Then, the substrate 2 was taken out from isopropanol, dried by a nitrogen blow, and UV ozone washed for 15 minutes.

[3] Next, a 10 g / L ethanol solution of a hydrate of the zinc acetylacetonate complex (manufactured by Sigma-Aldrich) was prepared. In addition, a 10 g / L ethanol solution of 2-dimethylaminopyridine (manufactured by Tokyo Chemical Industry Co., Ltd.) was prepared. The above two kinds of ethanol solutions were mixed in equal volumes to obtain a mixed solution.
The washed substrate 2 having the above cathode 3 was set in a spin coater. The above mixed solution was dropped onto the cathode 3 (surface to be formed) of the substrate 2 and applied by rotating at 2000 rpm for 45 seconds (coating step). The substrate 2 having the mixed solution coated on the cathode 3 was heat-treated for 30 seconds on a hot plate set at 120 ° C. in the air (heat treatment step). As a result, an electron injection layer 1 having an average film thickness of 5 nm composed of a mixture containing at least zinc oxide and 2-dimethylaminopyridine was formed.

[4] Next, a 1.0% by weight cyclopentanone solution of the boron-containing compound represented by the following general formula (1) was prepared. The substrate 2 formed up to the electron injection layer 1 was set on a spin coater, a cyclopentanone solution of the above boron-containing compound was added dropwise, and the substrate 2 was rotated at 3000 rpm for 30 seconds for coating. Further, the substrate 2 coated with the cyclopentanone solution of the boron-containing compound was annealed for 1 hour using a hot plate set at 150 ° C. in a nitrogen atmosphere. As a result, the organic electron injection layer 4 made of a boron-containing compound having an average film thickness of 30 nm was formed.

[5] Next, the substrate 2 formed up to the organic electron injection layer 4 was fixed to the substrate holder in the chamber of the vacuum vapor deposition apparatus. Bis [2- (o-hydroxyphenylbenzothiazole] zinc (II) (ZnBTZ2) represented by the following general formula (2), tris [1-phenylisoquinolin-C2, N] iridium represented by the following general formula (3) (III) (Ir (piq) 3), N, N'-di (1-naphthyl) -N, N'-diphenyl-1,1'-biphenyl-4,4'represented by the following general formula (4) -Diamine (α-NPD), N4, N4'-bis (dibenzo [b, d] thiophen-4-yl) represented by the following general formula (5) -N4, N4'-diphenylbiphenyl-4,4'- Diamine (DBTPB), 1,4,5,8,9,12-hexaazatriphenylene-2,3,6,7,10,11-hexacarbonitrile (HAT-CN) represented by the following general formula (6). , Al were put into the rutsubo and set in the vapor deposition source.

[6] The inside of the vacuum vapor deposition apparatus was depressurized to about 1 × ^10-5 Pa, and ZnBTZ2 was formed into a 10 nm film to form an electron transport layer 5. Further, ZnBTZ2 was used as a host and (Ir (piq) 3) was used as a dopant for co-depositing at 20 nm to form a light emitting layer 6. At this time, the doping concentration of (Ir (piq) 3) was set to 6% with respect to the entire light emitting layer 6. Next, the hole transport layer 7 was formed by forming a 10 nm film of DBTPB and further forming a 40 nm film of α-NPD. Next, HAT-CN was deposited with a film thickness of 10 nm to form a hole injection layer 8. Finally, Al was vapor-deposited to a film thickness of 100 nm to form the anode 9. Through the above steps, the organic EL element 10 was obtained.
When the anode 9 was vapor-deposited, a stainless steel vapor deposition mask was used so that the vapor-deposited surface had a strip shape with a width of 3 mm. As a result, the light emitting area of the organic EL element 10 was set to 9 mm ² .

<Comparison example>
By the method shown below, in the coating step of the step of forming the electron injection layer, an ethanol solution of zinc acetylacetonate complex hydrate (manufactured by Sigma Aldrich) of 5 g / L was used instead of the mixed solution. Manufactured an organic EL element in the same manner as in Examples.
The average film thickness of the electron injection layer was 5 nm.

(Measurement of light emission characteristics of organic EL element)
A voltage was applied to the organic EL element and a current was measured by a "2400 type source meter" manufactured by Keithley. Further, the emission brightness was measured by "LS-110" manufactured by Konica Minolta.

FIG. 2 shows the relationship between the applied voltage and the current density of each of the organic EL elements of Examples and Comparative Examples. As shown in FIG. 2, in the organic EL element of the example, a high current density is obtained at a lower applied voltage as compared with the organic EL element of the comparative example. As shown in FIG. 2, in the low voltage region of 3 V or less, a higher current density than that of the examples is obtained in the comparative example. This is because the organic EL element of the comparative example has a large leakage current that does not contribute to light emission. That is, it can be seen that the organic EL element of the example has a better emission characteristic as well as a suppressed leakage current as compared with the organic EL element of the comparative example.

Further, FIG. 3 shows the relationship between the applied voltage and the brightness of each of the organic EL elements of Examples and Comparative Examples. As shown in FIG. 3, in the organic EL element of the example, higher brightness is obtained at a lower applied voltage as compared with the organic EL element of the comparative example.

FIG. 4 shows the relationship between the current density and the external quantum efficiency of each of the organic EL devices of Examples and Comparative Examples. As shown in FIG. 4, in the organic EL device of the example, higher external quantum efficiency is obtained as compared with the organic EL device of the comparative example in any current density region. It is considered that this is because the organic EL element of the example has a suppressed leakage current and good light emission characteristics as compared with the organic EL element of the comparative example.

(Measurement of life characteristics of organic EL elements)
For the organic EL elements of Examples and Comparative Examples, the relationship between the elapsed time from the start of driving at a constant current and the relative brightness was investigated by an "organic EL life measuring device" manufactured by EHC. Specifically, the voltage is automatically adjusted so that a constant current flows through the organic EL element, and the relative brightness is measured with respect to the elapsed time from the start of driving at a constant current (Konica Minolta's luminance meter (brightness meter manufactured by Konica Minolta). LS-110)) was performed. The current value was set for each of the organic EL elements of Examples and Comparative Examples so that the brightness at the start of measurement was 1000 cd / m ² . The result is shown in FIG.

FIG. 5 is a graph showing the relationship between the elapsed time from the start of driving at a constant current and the relative brightness using the organic EL life measuring device. As shown in FIG. 5, in both the organic EL elements of Examples and Comparative Examples, the brightness decreases with the elapsed time. However, in the examples, the decrease in brightness is suppressed as compared with the comparative examples. For example, when the elapsed time is 700 hours, the brightness is reduced by about 180 cd / m ² in the comparative example. On the other hand, in the examples, the decrease is only about 60 cd / m ² .
From this, it was confirmed that the deterioration of the luminance when continuously driven can be suppressed by using the organic EL element of the example.

(Observation of surface shape of electron injection layer)
Using the "atomic force microscope (AS-7B-W)" manufactured by Takano Co., Ltd., the surface roughness on the surface of the electron injection layer formed on the cathode of the substrate during the production of the organic EL elements of Examples and Comparative Examples was measured. It was measured. The measurement range of the surface roughness was a square of 1 μm × 1 μm.
FIG. 6 is an atomic force microscope observation photograph showing the surface shape of the electron injection layer of the example. The surface roughness (Ra) of the examples was 1.30 nm.
Further, FIG. 7 is an atomic force microscope observation photograph showing the surface shape of the electron injection layer of the comparative example. The surface roughness (Ra) of the comparative example was 3.01 nm.

As shown in FIG. 7, in the electron injection layer of the comparative example, a large number of large aggregates composed of metal oxides were present in the electron injection layer. On the other hand, in the electron-injected layer of the example shown in FIG. 6, although agglomerates composed of metal oxides were present in the electron-injected layer, the number of agglomerates was smaller and the size was smaller than that of the comparative example. .. As described above, in the electron injection layer of the example, aggregation of the metal oxide was suppressed and a flat electron injection layer was formed as compared with the electron injection layer of the comparative example.

1 Electron injection layer 2 Substrate 3 Cathode 4 Organic electron injection layer 5 Electron transport layer 6 Light emitting layer 7 Hole transport layer 8 Hole injection layer 9 Anode 10 Organic EL element (organic electroluminescence element)

Claims (11)

The substrate, cathode, electron injection layer, light emitting layer, and anode are arranged in this order.
The electron injection layer comprises a mixture containing at least a metal oxide and a tertiary amine.
An organic electroluminescence device characterized in that the surface roughness Ra on the light emitting layer side is 2.5 nm or less. The organic electroluminescence device according to claim 1, wherein the metal oxide is zinc oxide. The organic electroluminescence device according to claim 1 or 2, wherein the tertiary amine is 2-dimethylaminopyridine. The organic electroluminescence device according to any one of claims 1 to 3, wherein a hole injection layer is provided between the light emitting layer and the anode. The organic electroluminescence device according to claim 4, wherein a hole transport layer is provided between the light emitting layer and the hole injection layer. The organic electroluminescence device according to any one of claims 1 to 5, wherein an organic electron injection layer made of an organic material is provided between the light emitting layer and the electron injection layer. .. The organic electroluminescence device according to any one of claims 1 to 6, wherein the substrate is made of a resin material. A display device comprising the organic electroluminescence device according to any one of claims 1 to 7. A lighting device comprising the organic electroluminescence device according to any one of claims 1 to 7. A method for manufacturing an organic electroluminescence device in which a cathode, an electron injection layer, a light emitting layer, and an anode are formed in this order on a substrate.
The step of forming the electron injection layer is a coating step of applying a solution containing a metal salt and a tertiary amine to the surface to be formed of the electron injection layer, and a heat treatment of the surface to be formed to which the solution is applied. A method for producing an organic electroluminescence element, which comprises a heat treatment step of forming the electron injection layer composed of a mixture containing at least a metal oxide and a tertiary amine. The method for producing an organic electroluminescence device according to claim 10, wherein the metal salt is a zinc acetylacetonate complex and the tertiary amine is 2-dimethylaminopyridine.